1. Field of the Invention
The present invention relates to hard coating film and optical elements having such coating film.
2. Description of the Prior Art
It is well known to form a hard coating film containing an organosilicon polymer on the surface of synthetic resin of high refractive index such as polyurethane resin and halogen-containing resin so as to improve scuff or mar resistance of the resin. It is also known to contain a particulate metal oxide of high refractive index in a hard coating film so as to inhibit formation of interference fringes on the synthetic resin of high refractive index having the hard coating film. As an example of the proposals to contain a particulate metal oxide of high refractive index in a hard coating film, Japanese Patent Publication No. 63-37142 discloses a hard coating film formed from a coating composition containing an organosilicon compound and a particulate tin oxide having an average particle size of 1 to 300 millimicrons.
The coating composition containing fine particles of tin oxide and an organosilicon compound disclosed in said Japanese patent publication, however, had the problem that said coating composition is difficult to treat or handle, because of the cohesive inclination or coagulation of the fine particles of tin oxide since the tin oxide particles are in a state of being charged positively while the organosilicon compound is in a state of being charged negatively in the composition.